The present invention relates generally to centrifugal analyzers for clinical laboratories, and, more particularly, to a washer for cleaning, and thus rendering reusable, disposable plastic cuvette rotors.
A number of fully automated centrifugal analyzers are currently used to perform various clinical tests using spectrophotometric techniques. All of the analyzers employ a so-called cuvette rotor that consists of individual analysis cuvettes connected together to form a ring. Multiple tests are simultaneously conducted by introducing different mixtures of samples and reagents into the individual cuvettes. During operation, the rotor is spun rapidly, thus forcing the reaction mixtures of samples and reagents into the outermost ends of the cuvettes, where they are optically analyzed.
Centrifugal analyzers that employ disposable plastic rotors have been particularly well received. A major advantage of rotor disposability is the absolute assurance that there will be no carryover between tests, i.e., within a given cuvette, there will be no contamination of a subsequent test by the specimens, reagents, and reaction mixtures of an earlier test. In return for this guarantee against between-run cross-contamination, disposability of the rotor increases the per test cost of consumables. It has heretofore been recognized that the added expense of disposability could be reduced if the rotors could be made reusable through washing and drying.
One proposal for a washer is discussed by Wu, A. H. B.; Ohneck, J. Klaus; E. McComb, R. B., in Clincal Chemistry, Vol. 28, 2188-89 (1982) and by Wu, A. H. B. and McComb, R. B. at Clinical Chemistry, Vol. 29.991 (1983). The described washer was specifically designed for cleansing the disposable cuvette rotors used in the Cobas-Bio centrifugal analyzer offered by Roche Analytical Instruments, Inc., of Nutley, N.J. 07110. The cuvette rotor employed in the Cobas-Bio centrifugal analyzer contains 30 identical cuvettes that are joined together in a ring. The innermost portion of each cuvette contains two well-like cavities or chambers, a large one for receiving the reagents and a smaller one for receiving the samples. These cavities are positioned side by side with their open ends facing upward and oriented about vertical axes that are arranged parallel to the axis of rotation of the ring. A reaction chamber having an inwardly facing open end extends outward along a horizontal axis that is oriented at right angles to the axes of the sample and reagent cavities. The axis of each reaction chamber is also oriented radially relative to the axis of rotation of the ring so that, upon acceleration of the ring, the samples and reagents are spun upwards and out of the sample and reagent cavities and into the outermost ends of the reaction chambers where they are contained for analysis. The washer described by Wu et al. consists essentially of two discs, having identical external dimensions, which are joined face to face and rigidly mounted in the center of a table-like base that is essentially a square platform having legs at each corner. An annular supply channel milled into the lower surface of the upper disc mates with the upper surface of the lower disc and is connected by generally straight channels with four jets provided at equidistant points about the circular periphery of the upper disc. In operation, the cuvette rotor is placed in an inverted position, in a resting position on the platform and over the hub formed by the interconnected upper and lower discs. In this inverted position, the reaction/sample chambers face downward. Water is introduced by way of an inlet provided in the bottom of the table, then travels through the supply channel in the upper disc and horizontally outward through the jets. Since the jets are angled relative to the horizontal reaction chambers of the cuvettes, the water flowing from the jets enters these horizontal chambers at an angle and, hence, provides a force that spins the rotor. As the individual cuvettes pass each jet, the reaction mixture of sample and reagents is rinsed.
The above-described washer has been shown to be effective for removing the residual results of enzymatic tests. The washer has not, however, proven effective in the removal of the residual results of endpoint tests. Thus, for such endpoint tests, there is unacceptable reagent carryover to subsequent tests. Accordingly, rotors that have been used in one endpoint test may not be reused in conjunction with other endpoint tests.
Since no special provision is made for catching and draining fluid from this washer, the used washwater cascades freely over the edges of the platform after cleansing the rotor. Accordingly, the washer must be located in a sink for operation. This requirement not only monopolizes what may be one of a limited number of available sinks, but also may require locating the washer at a distance from the analyzer, which is unacceptable, both in terms of inconvenience and the increased likelihood of spills. As well, the uncontained, vigorous flow of contaminated washwater presents the likelihood that the operator will be exposed to harmful aerosols.
The foregoing washer ahso disadvantageously uses a significant quantity of water during the normal wash cycle. For example, about 32 litres of water is needed for a five-minute wash. Where deionized water is used as the cleansing fluid, such consumption is particularly costly.
The present invention provides an improved washer that overcomes the disadvantages of the developments described above. In particular, an important aspect of the invention is the provision of an arrangement of cleaning jets that assures good turbulence of the washing fluid within the cuvette chambers while, at the same time, providing rapid rotation of the ring. In accordance with a further aspect of the invention, a regulator controls both the pressure and duration of the flow to the jets and, thus, facilitates the development of, and adherence to, operating products, while also minimizing the amount of fluid consumed during a wash cycle.